CHM 332 Lecture 8
Dr D Chemistry Videos・27 minutes read
Enzymes are critical proteins that facilitate reactions by lowering activation energy barriers and increasing reaction rates through specific mechanisms and structures, such as active sites and catalytic triads. The lecture highlights enzyme chemistry, discussing criteria for reactions, catalysis mechanisms, specificity pockets, and the role of cofactors and coenzymes in enhancing enzyme activity.
Insights
- Enzymes are biological catalysts that accelerate chemical reactions by lowering activation energy barriers, increasing reaction rates significantly compared to uncatalyzed reactions. They achieve this by providing a conducive micro-environment in their active sites, optimizing conditions for reactions to proceed efficiently.
- Catalysts such as enzymes operate through specific mechanisms like the catalytic triad of serine, histidine, and aspartic acid, which work together to enhance reaction specificity and efficiency. Enzymes draw reactants into their active sites, ensuring proper orientation for reactions while interacting with transition states more effectively than substrates, showcasing their intricate structural and functional design for catalyzing diverse biochemical reactions.
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Recent questions
What are enzymes?
Proteins that catalyze chemical reactions in organisms.
How do enzymes increase reaction rates?
By lowering the activation energy barrier.
What is the role of catalysts in reactions?
Increase reaction rates by lowering activation barriers.
How do enzymes differ from isozymes?
Isozymes have different amino acid sequences but catalyze the same reactions.
What determines the spontaneity of reactions?
Free energy diagrams based on energy levels of products and reactants.
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Summary
00:00
"Enzyme Chemistry: Catalysts for Reaction Acceleration"
- Lecture focuses on enzyme chemistry, a critical class of proteins.
- Enzymes are biomolecules that facilitate reactions by catalyzing various chemical reactions.
- Three criteria for two species to react: contact, proper orientation, and sufficient energy.
- Reaction diagrams illustrate the transformation of reactants to products through an activation barrier.
- Activation energy height determines reaction rate; lower barrier leads to faster reactions.
- Increasing collisions can speed up reactions by altering concentration, temperature, or frequency of contact.
- Diagrams show potential energy differences between reactants and products, indicating thermodynamic favorability.
- Free energy diagrams determine spontaneity of reactions based on energy levels of products and reactants.
- Catalysts increase reaction rates by lowering activation barriers without changing energy of reactants or products.
- Enzymes are biological catalysts that catalyze various reactions, with ribozymes also playing a similar role.
13:46
Enzyme Functions and Catalysis Mechanisms
- A cofactor is a small organic or inorganic molecule not bound to the enzyme.
- A coenzyme is a small organic molecule loosely bound to the enzyme.
- A prosthetic group can be a metal or small organic molecule tightly bound to the enzyme structure.
- Enzymes catalyze addition, removal, and rearrangement reactions.
- Isozymes differ in amino acid sequence but catalyze the same type of reaction.
- Enzymes are named after their function with an -ase suffix.
- Enzymes work through active sites, reaction specificity, and regulation.
- Enzymes increase reaction rates significantly compared to uncatalyzed reactions.
- Equilibrium constants and free energy are crucial in enzyme reactions.
- Enzyme catalysis mechanisms include acid-base, covalent, and metal ion catalysis.
27:38
Enzymes: Catalysts of Specific Reactions
- The catalytic triad in enzymes consists of serine, histidine, and aspartic acid, with serine's side chain cleaving the peptide bond, histidine enhancing serine's nucleophilicity, and aspartic acid stabilizing histidine.
- Enzymes are large to facilitate contact, orientation, and sufficient energy for reactions, with the active site optimizing conditions for reactions to proceed through stabilizing the transition state.
- Enzymes draw reactants into the active site, ensuring proper orientation for reactions and creating a conducive micro-environment that eliminates competing reactions in the solvent.
- Enzymes like peptidase interact with transition states more effectively than substrates, with the catalytic triad of serine, histidine, and aspartic acid being crucial for peptide cleavage reactions.
- Enzymes have specificity pockets that interact with substrates beyond the active site, determining which peptide bonds are cleaved based on the nature of the pocket.
- The lecture provides an overview of how enzymes function by facilitating reactions, setting the stage for discussions on kinetics and measuring reaction rates in the next lesson.
